Serial Interface System RS 422 SYNMET / NAV (SCH 664) - Windaus

Operating Instructions
Serial Interface System (SCH 664)
1.0 Description
1.1 General
The interface box SYNMET-NAV model SCH 664 is designed to convert up to twelve analogue and 5 digital channels
(pulse and event) of various meteorological sensors into a digital signal of RS 422 standard with a message format
according to the NEMA 0183 requirements which are world wide in use for all naval electronic systems.
Regarding the wind parameters the system in general is measuring the relative data which are influenced by own speed
and heading of the vessel. As an option the system can be enabled to calculate true wind data when receiving
corresponding information contained in the "own ship data" or OSD protocol of the NMEA message.
In the standard version two serial ports COM1 and COM2 are implemented as 1 * RS 422 for continuous data
transmission and 1 * RS 232c or RS 422 for service and maintenance. On request the system can be extended with an
option containing four more serial outputs COM3 to COM6 by means of a piggy-back-module.
All generated digital output signals can used for a transfer to other intelligent peripheral control systems as auto pilot
devices or others.
Its is constructed as a primer coated seawater resistant aluminium housing which normally is coated with grey (RAL
7001) lacquer. The performance of lacquering corresponds to the general demands for military equipment.
To fulfil the strong EMC/EMI requirements the housing is equipped with conductive rubber sealings and metallic cable
inlets according to VG 88 812.
1.2 Functional description of sub-components
The interface system SCH 664 NMEA (SYNMET-NAV) in general is consisting of the sub-components power supply PS,
controller-board CPU, sensor interface SI and a motherboard. Corresponding designations are printed on the front
panels of the boards.
1.2.1 Sensor interface board SI
Incoming analogue signals from the sensor first get linked to the sensor interface board SI where an adaptation
potentiometer for the DC-generator and a DC-DC-module for the supply of the N18-ring potentiometer are located. For
service purposes it can be set to a corresponding mode by means of a mini-switch on the front panel.
1.2.2 Controller board CPU
On the controller board CPU the analogue signals of the SI board get converted with a resolution of 12 bit, evaluated and
processed from an advanced micro-processor system (controller) NEC V25. A user specific firmware written in "Turbo
Pascal" carries out the signal processing including plausibility checks, compensation of error effects (e.g. the threshold
and non-linear behaviour of the cup rotor) and creates user-specific digital message formats (e.g. NMEA 0183) to be
linked to other equipment. In general the controller starts again automatically after switching on the power supply of the
system or if firmware errors occurred. Manual resets can be carried out by means of a small push button on the front
panel.
1.2.3 Power supply board PS
The electronically controlled power supply insert PS can be operated in the wide range of 100 to 240 V AC and
frequencies of 50....60 Hz without any manual configurations. Various LED's are indicating its correct operation. For
service purposes the AC and DC circuits can be switched independently on & off by means of two micro switches on the
front panel.
1.2.4 Digital-to-analogue converter
An optional digital-to-analogue converter module (DAC piggy-pack) located on the CPU board provides external
instruments like wind indicators and/or interfaces with corresponding signals of a 0 to 10 volts or 0/4 to 20 mA output.
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